The present invention relates generally to threaded fastener means and more particularly to certain new and useful improvements in the quick mounting of such fasteners to moldable structures, such as injection molded electrical assembly boxes, made of a non-metallic or plastic material.
In residential, commercial and apartment construction, it is often desirable to utilize various relatively light, load-bearing structures, such as electrical assembly boxes, including electrical junction boxes or electrical outlet boxes, for conveniently mounting outlet receptacles, switches and the like to walls or ceilings. It is therefore desirable to design such structures for inexpensive and relatively simple fabrication by modern injection molding techniques with non-metallic or plastic materials. However, disadvantages are encountered where it is necessary to mount receptacles, switches or other devices to such structures with threaded fasteners. In order to provide suitable means for engaging such threaded fasteners, integral with the mounting structure, it would necessitate either a relatively complicated and expensive molding operation or an inconvenient second tapping operation to form a threaded borehole or the like.
In addition, it has been found that by providing internal plastic threads in such structures, performance has been unsatisfactory since the threads tend to be easily "stripped", rendering the entire structure completely useless. This is of particular importance where it is anticipated that the threaded fastener may be repeatedly removed from and re-threaded into the borehole, such as in electrical assembly boxes, since, during installation, the electrician may have to insert and remove the threaded fastener several times for complete and proper installation of the receptacle, switch, etc. Moreover, during the useful life of the box, the fasteners may be removed several times for replacement of malfunctioning parts. Furthermore, since electrical assembly boxes, especially the threaded fastener mounting portions thereof, tend to be mounted to beams, etc., where access is limited, the initial seating required, as well as complete turning down of the screw may prove exasperating and time-consuming for the installer.
Some prior art structures include tubular inserts that are force-fit into pre-molded openings in the box and which include thread engaging portions extending into its interior for engaging the threads of the fastener at substantially one point. However, although such devices have proved adequate for some applications, they may not be sufficiently reliable or strong for certain applications, such as, use in ceiling boxes where the threaded fastener is subjected to constant axial loading.
It is therefore an object of the present invention to provide a new and improved threaded fastener mounting means.
Another object of the invention is to provide a new and improved threaded fastener mounting means which permits threaded fasteners to be quickly and easily mounted to structures made of a moldable plastic material.
It is also an object of the present invention to provide a new and improved fastener mounting means whereby threaded fasteners may be securely and tenaciously fastened to structures made of moldable plastic materials.
It is a further object of the invention to provide a new and improved threaded fastener mounting means capable of engaging a threaded fastener to support a continuous loading.
It is yet another object of the present invention to provide a new and improved threaded fastener means which will not be rendered useless by improper insertion of a threaded fastener.
Objects and advantages of the invention are set forth herein and in part will be appreciated herefrom or may be learned by practice with the invention, the same being realized and attained by means of the structures and combinations pointed out in the appended claims.
The present invention consists in the novel parts, constructions, arrangements, combinations and improvements herein shown and described.